1. Field of the Invention
The present invention relates to a method for treating a Cu thin sheet.
2. Description of the Related Art
Electrical contact materials, e.g., motor brushes, are required to have various types of additional durability, e.g., abrasion resistance, stress relaxation resistance, corrosion resistance, and weatherability, besides basic characteristics, e.g., electrical conductivity and mechanical strength, in accordance with the use of parts. In many cases, these various types of durability are locally required at a special position around an area serving as a contact. In such a case, usually, plating, roll cladding, thermal spraying, or the like of a different type of material is applied to a whole base material to produce a thin sheet composite material and, subsequently, an electrical contact is obtained by press-cutting or bending. This is because, in many cases, the cost contrarily increases by producing a local composite material at a specific position through masking or the like. However, it is necessary that the part design of the electrical contact which is a composite material as a whole be performed on the basis of the basic characteristics of the composite material, and there is a disadvantage that the part design on the basis of the known material characteristics of a commercially available alloy serving as a base material is not utilized on an as-is basis.
In this regard, PTL 1 discloses a method for attaching a metal powder to a base substance by using a laser. Specifically, in the disclosed method, a design region on the base substance is covered with a mixture in which granular silver is mixed with lamp black, the resulting mixture is irradiated with a laser and, thereby, a buildup layer is formed locally. According to this method, a base substance locally reinforced by a buildup layer containing silver as a primary component can be obtained.
Meanwhile, PTL 2 describes a method in which a powder containing a metal and a reinforcing material is supplied to a substrate, the powder is heat-melted by application of a laser and, thereafter, cooling is performed, so as to form an article having a fine-grained structure. Nickel and nickel alloys are shown as examples of metals, and borides and carbides are shown as examples of reinforcing materials. It is also possible by this method to obtain a base substance locally reinforced by a buildup layer of a fine-grained structure.
Furthermore, PTL 3 describes a method in which a mixture produced by mixing 80 to 99 percent by mass of powder containing 7 to 20 percent by mass of Ni and 1 to 20 percent by mass of powder containing Mo and Co is built up by a laser. It is also possible by this method to obtain a base substance locally reinforced by a buildup layer.